Various types of laminate sheets have widely been used in practical fields, and have been required to possess diverse properties according to use. The properties required for many packaging materials including photosensitive materials are that they are hard to break and curl, have large impact resistance and flexibility, are susceptible to heat sealing for sealing, and the like. The realization of cheap, sealable, seal-packageable and difficult-to-curl laminates having improved tensile strength, Gelbo test strength, drop strength and resistance to impact without deteriorating certain properties such as cushioning, flatness and slip properties would lead to opening up new avenues for use, for instance, finding use in the packaging of photosensitive materials with such laminate sheets, said photosensitive materials having so far been packaged in sealed metallic containers for transportation. In addition, such laminate sheets are expected to offer practical advantages, e.g., be used to control moisture-proofness and gas barrier and be effective in reductions in weight of packages and prevention of breakage thereof. The present applicant has already disclosed such packaging materials in Japanese Patent Kokai Publication No. 57-6754 (U.S. Pat. No. 4,331,725).